Voltage comparison apparatus



" March .5, 1946.-

M. H. scHRENK ET AL v VOLTAGE coMPARe-ON APPARATUS Patented Mar. 5, 1946 vol-.TAGE COMPARISON APPARATUS lVIatthewH.` `Schrenk andGeorge. Schleier,

' Washington, D. C.

Application July 14, 1941,-seria1 No.. 402,426

(o1. irse-18e) (Granted. -under the. act of March` 3 1883as amended April 3,0, 1928i; 37!)y 0..-Gr.,757.).

' 8 Claims.

rents to be utilized for comparison by the joint l action of the voltages to be compared and pote-ntials synchronized with other potentials;

To. provide apparatus of the type mentioned that is adapted to use with eithery an alternating current or a `direct current indicator.

Other objects will be apparent to thoseskilled in this art from the following description when read in connection with the accompanying drawingy wherein: v

Fig. 1 shows `schematically a form of our invention particularly adapted for use with an alterhating current indicator;

Fig.v 2 depicts our invention modified for use- With a direct. current indicator.

It is frequently desired to comparev the ampli-- tudesv of two voltages either from the same source when received through different collecting and amplifying means or when one is derived from a standard of known amplitude and the other is from a source to be compared or calibrated. Likewise, the wave forms of two voltages must frequently bey compared to determine features or similarity or difference. The present invention provides means for such comparisons.

In Fig. 1 the push-pull audio oscillator, designated as a whole by the reference 3, includes an inductance 4 in its output circuit to which is,

coupled a seco-nd inductance- 5, whereof the ter minals. are respectively connected to anod'es G and 'l of rectifier 8. The resistances 9 and I I1 are respectively in series with cathodes II and I2 of the rectifier 8. Screen grids I3 andy I4 of pentode vacuum tubes I 5 and I6 are respectively connected to the high potential sides of resistances 9 and I0 and anodes I1 and I8 of thepentode tubes have a common output I9.

Control grids and 2| of tubes I5 and I6 are connected to tuned input circuits 22' `and 23j whereby the, voltages to be compared areappli'ecl to the respective tubes. It is to be understoodthat tubes I5 and |56 need.' not necessarily be pentodes and th'atwhileinputs 22 and`23 are preferablytuned forcomparing radiofrequency voltages,` they :may be untuned. Sensitivity control resistanoes 24 and 25 are respectively connected to cathodes 26 and k2'I o'f tubesv I5 'and I6`and have 'a 'common' connection to grounded at 28. The inductance 29 is also coupled to inductance 4 of' oscillator 3 and; `hasy its terminals connected by leads 38 and 39 either to one of the coilsl 40 ofy an f alternating current indicator 4I of the eIectrodynamo-meter type having an index that can swing to either side of' a median rero point for comparing amplitudes of voltages, or they may be connected to the deiiec'tiony plates of a cathode ray. tube 'for comparing either the amplitudes or the wave forms of thefvoltages impressed upon tubes I5 and I6 through inputs 22 and 23. `Out-v put I`9'may be connected to the input of suitable amplifying means 42, when the voltages to be compared are small, the output 4'3 of `such amplifying means being connected to the other coil 44 of the indicator orv if the voltagesl to be compared are of suiiicient strength, output I9 may be direetly` connected to coil `44p. Y

It will, of course, be understood that any lsource of alternating current of suitable frequency Vmay be substituted for Vthe oscillator 3,` and that the frequency of such current should be high enough that so, long as the inputs to an indicator of the electro'dynamometertype are equal on both half' waves the index of the indicator -will not follow the alterations of' the current but will remain atv zero.

The operation of this form of our invention is as'. follows: Y

The potentialsv developed across resista-hoes` 9 and I0 are alternately applied to screen grids I3'.

and I4' to swing these grids positive, and each of these potentialsis synchronized with the application of potential in a denite direction to the indicator connected to inductance 29, and thus the index of suchindicator will tend always rto swing in the same direction each time a positive potential is kapplied to one of the screen grids and in the opposite direction each time a positive potentialis applied' to the other screen gnid.

grid 2l the input to the indicator will be greater during that half wave that tube I is passing current, and hence the index of the indicator will be movedin the direction it is urged during the passage ci current through tube I5. When the voltages are to be compared as to Wave form the pattern on thegcathode ray tube' screen'will inductance 4 by inductances 34 and 35 and output terminals 45, 41 of amplier d2 are connected to cathode 36 of rectiiier 33 through jack aLwhich is grounded at 4B. The output leads-38f35of rectifier 33 may be connected to D. C. indicator 48 which is provided with a grounded potentiometer type resistance 49. It is apparent that the outputs from theanodes 3| Yand 32` will. be synchronizedwith the passinglof current through tubes ISandIG.

In Fig. 3 is shown the manner-in which the circuit of Fig. 2 may be connected to the deflection plates of a cathode-ray oscillograph. The output leads 38, 39 of rectifier 33 are connected to one .pair of plates, while of the other pair one is grounded atEIJ and the other is connected to the cathode 3E of rectifier 33. The output termix nals d5 and 'l are connected to jack 31 as before. The cathode-ray oscillograph may be used in connection with the circuit of Fig. 1 in the same manner.A The leads 38 and 39 Will be connected to one pair of deflection plates as shown in Fig. 3 while the lead 43 will connect to one plate of the other pair, the remaining plate being grounded. It should be understood that thev practice of the invention is not limited to the embodiments illustrated and described. but is circumscribed only by the scope and limitations of the `appended claims. The invention described herein and claimed may be usedand/or manufactured'by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

We claim: 1. Voltage comparison apparatus, comprising a push-pull oscillator having an output circuit including an inductance, a rectifier having two anodes respectively connected `to opposite ends of said inductance and two cathodes respectively cooperating with said anodes, a resistance in series nately in opposite senses, means to derive from each sense a separate positive potential; two vacuum tubes each having a screen grid connected to have a respective said positive potential applied to it, a cathode, a control grid, and an anode; van input circuit for a voltage to be compared connected to each of said control grids, a common output circuit connected to the anodes of said tubes, and means to derive from said oscillator opposite potentials each of which is respectively synchronized with the positive potential applied to one of said screen grids.

3. Voltage comparison apparatus, comprising a push-pull oscillator whereof the output is alternately in opposite senses, means to derive from each sense a separate positive potential; two vacfull wave rectifier 33 are respectively coupled to A uum tubes each having an electrode connected to have a respective said positive potential applied to it, a control grid and an output electrode; an input circuit for a voltage to be compared connected to each of said control grids, a common output circuit for said output electrodes, and means to derive from said oscillator opposite potentials each oi which is respectively synchronized with the said positive potential applied to one of said tubes.

' 4. Voltage comparison apparatus, comprising a source of low frequency alternating current, means for deriving a potential from each half wave of said current; two vacuum tubes each connected to be controlled by the joint and simultaneous action of a respective one of said lpotentials and a separate voltage to be compared, a common output circuit for said tubes, and means to derive from said source opposite potentials each of which is respectively synchronized with the passing of current by one of said tubes.

5. Voltage comparison apparatus, comprising two vacuum tubes, means toV apply to each of said tubes a separate voltage to be compared, a second means to apply to each of said tubes alternately a potential to cooperate withthe respective one of said voltages to cause Vthe tubes to pass current, a common output circuit forA said 'with each said cathode, a common ground connection for said resistances; `two vacuum tubes each having a screen grid respectively connected tothe high potential side of one of said resistances, an anode, acathode anda control grid; a tuned input Vcircuit for' a voltage to be compared connected to each said control grid, a commcn output circuit connected to the anodes of tubes, means to derive from said second means potentials each of which is respectively Asynchronized with the application to each tube of a first mentioned potential, and means to combine the output of each tube with the respective'potential from said second means.

6. Voltage comparison apparatus, comprising a push-pull audio oscillator having an output circut including an inductance, a rectiiier having two anodes respectively connected to opposite ends of said inductance and two catho'des respectively cooperating with said anodes, a resistance in series with each said cathode, a common ground connection for said resistances; two vacuum tubes each having a screen grid respectively connected to the high potential side of one of said resistances, an anode, a cathode and a control grid; a tuned input circuit for a voltage to be compared connected to each said control grid, a common output circuit connected to the anodes of said vacuum tubes, a sensitivity control resistance connected to each said cathode, a common ground connection forsaid sensitivity control resistances, and a full wave rectiiier coupled to the output circuit of said oscillator, the output of said rectiiier on each half wave being respectively synchronized With the output of one of said tubes to be combinable with the output of the respective said tube toy actuate an indicator.

7. Voltage comparison apparatus, comprising a source of low frequency alternating current, means for deriving a potential from each half wave of said current; two vacuum tubes each connected to be controlled by the Joint and simultaneous action of a respective one of said potentials and a separate voltage to be compared, a common output circuit for said tubes, and a full wave rectier coupled to -said source, the output of said rectiiier on each half wavebeing respectively synchronized with the output of one of said tubes to be combinable with the output of Y the respective said tube to actuate an indicator. 8. Voltage comparison apparatus, comprising means providing two separate electron streams,

means for applying each oi' the voltages to be compared to control in part the ow of a respeci tive one of said streamsfmeans separately protherewith.

MATTHEW` H. SCHRENK. GEORGE C. SCHLETER. 

